[Andy Smith]

I just thought of another piece of information that would be useful. The stock exhaust size. It appears that until the 2nd cat we have 2.25 inch piping (or 55mm) and after the cat it goes to 2inch (50 mm) piping. Strange? I thought so...

 

[StickShifter]

...Actually, its not that strange in theory...The further the exhaust gets away from the engine, the cooler it gets...Cooler exhaust condenses and therefore slows down...By decreasing the exhaust size, it allows the velocity to stay higher...Higher exhaust velocity is what builds torque...
...Now, if the factory exhaust system wasnt so screwed up, it would be a pretty good idea...It would be more effective in a properly designed system...

 

[sabre]

hrm sweet, would the Magnaflow catback work without any problems on the 2.3l?

Or should I wait for the FS Exhaust? Thanks

 

[Andy Smith]

hrm sweet, would the Magnaflow catback work without any problems on the 2.3l?

Or should I wait for the FS Exhaust? Thanks

From what I see none of the popular exhausts will fit. The only two that have a shot in my eyes are the Trubendz rear can style or the vibrant maybe. The rest dont have a snowball's chance in hell. Plus you'll need a grinder as shown in my other thread about exhaust.

 

[sabre]

Back

With the higher exhaust velocity in mind, if I were to do the mod stickshifter did and chop off the farthest back rear res/muf, when welding on the tip would it be better to keep it 2"(50mm) or would it make any difference in this application?

Thanks

 

[StickShifter]

The tip size wont really make a difference in anything but the sound...A larger tip will make it deeper, and smaller will increase the pitch...
...You could go into the fact that a larger tip will cause the exhaust gas to become turbulent as it exits the smaller pipe, and therefore the velocity should decrease, but since the tip is so short, it becomes almost a moot point...It is this slowing of the gases in a large tip that causes the deepening of the exhaust note, however...
...And, the transition from 2.25 into 2" pipe isnt very smooth...Its actually a 'step' right after the second cat...It induces some turbulence into the exhaust flow...If it was a smoother transition, my ramblings about velocity and flow and such would be much more valid...I was merely proposing theory...
Go nuts with the tip size...For all intents and purposes, it wont make a difference in velocity...

 

[sabre]

Excellent, thanks for the great info. It makes sense too, I'll probably stick with 2.25 tip. Until I can get a complete 2.5" catback. Going to talk with Trubendz to see if they can provide a pzev solution. Thanks.

 

[moshaholic2]

Until I can get a complete 2.5" catback.

From my personal experiance (VW's) 2.5" on a small engined NA car is too big in all but high RPM race situations where you dont need the torque as much.

The PZEV does have more torque than the Zetec, but it's still not that much of a rocket.

2.25" should be more than adaquate. It will flow quickly, and have enough back pressure to create some torque.

 

[Chezterr]

As far as exhaust systems go... I would have to agree that using 2.25" piping on a PZEV still using the stock exhaust manifold is the way to go. If you install a 4-1 race header that has a 2.5" exit flange (like ours) then you should go with a 2.5" mandrel bent system.

We will more than likely offer a cat back exhaust as well as a header back exhaust. Many muffler shops wont remove the second cat in the system. And for an exhaust system to be street legal, you need to keep the factory cat installed. Deciding how we will leave the factory cat installed and design a kit around it is still to be determined.

Nikolas

 

[StickShifter]

2.25" should be more than adaquate. It will flow quickly, and have enough back pressure to create some torque.

...2.25" is ideal, but not because of the back-pressure...Back-pressure is bad, no matter the situation...Back-pressure does in no way create torque...Velocity is what creates torque/power...

...So, to summarize...Back-pressure is bad...Velocity is good...2.25" is good for a stock engine that is used on the street...

...Any questions, PM me to discuss, and I will get more technical...

 

[method213]

so it would be nice to change the pipe from the Second cat to 2.25?? peace

 

[StickShifter]

Yep...If you are careful, you can trim the stock pipe close to the exit of the second cat (right before it necks to 2"), and add 2.25" from there...This will give you 2.25" all the way through...Except the flex-pipe, of course...But thats another story...

 

[method213]

ohh, cause ill probably put on of those cheap exhaust from ebay, while ill wait for Real cat-back's exhaust to come out, peace

 

[moshaholic2]

ohh, cause ill probably put on of those cheap exhaust from ebay, while ill wait for Real cat-back's exhaust to come out, peace

why waste your $$$? If you are that desperate to do an exhaust mod, do what others have done, cut off that big heavy rear resonator and have someone put in new pipe for $40.